The present invention relates generally to an electronic device for an automotive vehicle, which device includes an electronic control device, various digital indicators, various vehicle condition sensors and so forth. More particularly, the invention relates to the electronic device with a self-monitoring capability for checking input and output conditions of respective electronic elements or segments.
Recently, it has become popular to employ a microcomputer in automotive vehicles to control vehicle operations such as engine control, anti-skid control, or to display various vehicle information such as warnings of abnormal conditions of vehicle devices. On the other hand, the automotive vehicle contains various devices such as the ignition system and the audio system which act as sources of noise which can possibly cause microcomputer failure. Furthermore, due to rather hard vibrations applied to the vehicle, the microcomputer itself or sensors serving as input devices can produce erroneous signals.
In the case of engine control, failure of the microcomputer operation influences fuel economy, engine performance and/or drivability and so on. Furthermore, in the worst case, failure of the microcomputer may cause uncontrollable engine operation resulting not only in damaging of the engine but also in serious danger to vehicle occupants.
In order to prevent the automotive electronic device from malfunctioning, it is, therefore, necessary to sequentially or continuously check each of the functions of the microcomputer to detect failure or error therein.
Conventionally, there are various self-monitoring automotive electronic devices. For example, British Prepublication No. 2,035,633, published on June 18, 1980 discloses a malfunction-preventing system for a microcomputer system which detects an abnormal condition in the program execution to produce an alarm or reset signal to automatically restart the computer. The malfunction-preventing system is applicable to automotive engine control wherein the microcomputer is capable of returning to normal operation upon detecting a malfunction of a program for fuel parameter calculation, thereby keeping the automotive engine control in order. In addition, British Prepublication 2,046,964, published on Nov. 19, 1980 and U.S. Pat. No. 4,339,801, issued on July 13, 1982, disclose an automatic control system for an automotive vehicle employing a microcomputer. In the control system, various check programs for checking each functional areas of the microcomputer and sensors for inputting control parameters have been provided to detect fault in any of these functional areas.
Furthermore, an external check system for factory use has been disclosed in U.S. Pat. No. 4,402,217. In this patent there is disclosed an electronic engine control system with a checking unit for sensors and actuators. The checking unit utilizes the microcomputer as a control unit and is releasably connected to the latter. The system comprises an engine assembly including an air intake, a throttle valve, an intake manifold, exhaust system and a combustion chamber, a sensor means determining an engine operating parameter and generating a sensor signal indicative of the determined engine operating parameter, a control means processing the sensor signal and generating a control signal corresponding to the engine operating parameter represented by the sensor signal, an actuator responsive to said control signal to control the ratio of energized period and deenergized period depending on the duty cycle of said control signal, a check unit cooperative with the control means for generating a command which causes the control means to affect the checking operation, the check unit including a selector means for selecting an item to be checked, which selector means is manually operable to cause the control means to affect the checking operation for the selected item, and a display means incorporated in the check unit for displaying the result of the checking operation.
The present invention is to improve the convenience of checking of these previously developed automotive microcomputer monitor systems. One particular feature of the present invention is that the self-monitoring system for the automotive electronic control system is associated with another microcomputer system with a display unit for displaying the results of the check operation.